Spark plug



J. M. ATWATER.

SPARK PLUG.

-APPLlCATl0N FILED APR. 29, 1920.

Patented Feb. 14, 1922.

L/i I u sp ark STATES- PATENT OFF-ICE.

30111? M. ,ATWATER, OF CHICAGO, ILLINOIS.

SPARK JPLUG.

Specification of Letters Patent.

Patented Feb. 14, 1922.

application filed-April 29, 1920. Serial No. 377,668.

the constantly changing character thereof,

its reluctance to vaporizing, and for many other reasons is called uponto perform heroic service in order to function properly,

.nd regulerly. It is an acknowledged fact hetrarely, if ever, do sparkplugs function at their best for any length of time. Even when initiallyinserted, the average spark plug functions so poorly-as to beaccountable, in a large measure, for the pobrfuel economy-end low engineeliiciency, so often obtaining.

It is an object of my inventionto provide plug; construction which, inoperation, shell pro iuce e spark better adapted to ignite the fuel inan internel combustion engine, and which shall function regularly andcoi'isistcntly in such manner.

1ft else an object of my invention to proulug construction which, inion, s produce a spark of great th, thus enehling it to functionpropnder sue! adverse conditions as are de-r provided with fuel that isd'iflicult ute, and under numerous other conditions inin'iiczil to theproper functioning of a. spark plug: as heretofore constructed.

Another object of my invention is to pro vide a spark plugconstructionwhich when once conditioned in n predetermined manner .alilapted toensure the best results shall maintain. this desired status against theinnumersble conditions tending to destroy or alter this predete minedind desired status.

Again provide be u s ii-l plug" construction which bination of the namedobjects, together with others that will I appear hereinafter, are

- with in on oil saturated cylinder, in it object of my invention to benecessary to produce a condition adapted to ensure the best functioningwith a. predetermined engine and its complen'ientary electrical system,or as'may be necessary after a. long period of use.

Other objects of my invention are to provide a spur: plug constructionthat can be manufactured and assembled quickly, and at low cost, andwhich shall be of a. form conveniently adapted for use in standardinternal combustion engines.

My invention consists generally in the form, arrangement, constructionand compzirts whereby the above attainable; and my lnvention will bemore readily understood by reference to the accompanying drawings whichillustrate the preferred embodiment thereof.

In said drawings:

Fig. 1, is a central sectional view of a spark plug constructionembodying my invention; and

l ig. 2, is a view of certain of the parts thereof disassembled, butarranged in the order of assembly.

The shape, form, and configuration of the spark plug parts may var Ithrough a wide range and the particular form and arrangement shown inthe drawings should, therefore, be considered as by way of illustrationand not by way of limitation.

Referring now to Fig. 1, 2 is a metallic shell provided with screwthreads 3 so that it may be screwed to the engine cylimler inwell-knownmanner.

lain insulator which shell 2, in the present instance, being heldagainst H, gas-tight packing washer 5. by means of a threaded bushing 6,which open ates against a seat washer 7 which, in turn, engages theshoulder 9 of the porcelain insulator. 10, is the side electrode whichis permanently allixed to the metallic shell 2. There is no particularnovelty in the ports thus far described other than the porcelain part 4,and they have been shown only for the purpose of better illustrating themanner iniwhich the partsconstituting the invention function.- I

4-, represents at porcels positioned in the all The porcelain element 4,as here shown, is provided with a long lower central opening 11, whichmerges with a larger opening 12, and which, in turn, merges into a stilllarger opening '13 that extends to the top 14.- of the porcelainelement. The openings 11 and 12, as here shown, are of smoothcylindrical form whereas ,the opening 13 is provided with screw threads13. 15 represents what 1 term the lower central electrode and it ispreferably cylindrical in form and of a size slightly smaller than theopening 11, thus providing an annular intervening space 16. To the upperend or" the lower central electrode 15 I permanently secure a member 17which member will hereinafter be termed a shell. The lower centralelectrode 15 is preferably formed of a hard tough metal such as a nickelmanganese alloy whereas I prefer to form the shelLot a relatively softmetal such as brass. have, by expel-L mentation and research, learnedthat it is essential to the functioning of the device that the unionbetween the shell and the lower central electrode shall be a gas-tightunion. it is also essential. that the parts shall be accurately alignedin order that the proper positioning of the lower central electrodeshall take place and its desired spaced relation to the wall of theporcelain insulator be assured. To thesecnds, I prefer to reduce theupper end otjhe electrode 1:). as indi catcd at 12), thus providing aseat 90 against which the element 17 can be forced. The lower part/ofthe shell 17, in turn, is provided with a central opening 18 ofconsiderable length. The relative sizcs of the opening 17 and the upperreduced portion 19 of the electrode l5 are such that the shell 17 can beshrunk upon the reduced port-ion 19, as indicated. Thus a nice aligmncntot' the parts is sccurcd and a gas-tight joint etl'ected. last it bethought thatcxpansion of the parts, due to the temperature conditionsprevailing in usc, would cause this joint to leak, I wish to state thatthe electrode 15 projecting as it does into the zone of the most intenseheat is raised to a considcrable higher temperature than that of theshell 17 so that the conditions met with in use not only tend not todestroy the gastight joint, but they actually result in the tighteningof this joint, due to the grcatcr expansion of the electrode portion 19.The upper portion of the shell 17 is provided with a, chamber 20 andinto this chamber depends what I term the upper central electrode 21extending into close proximity to the upper end of the lower electrode15 thus providing a small gap 22.

Due to different conditions prcvailingin difi'erent internalcon'ibustion engines or inthe same internal combustion engine because ofthe changing character of the electrical ignition system, as well aschanging con- -and bv turnin (litions which take place because ofordinary wear and tear, I find it desirable to provide means foradjusting the spaced relationof the upper and lower electrodes, 1. e.toprovide means for varying the size of the gap, 22. To this end, 1thread the upper part of the upper electrode, 21, as indicated at 23,and mount it. in the internally threaded bushing 2-4;. Thus by turningthe electrode, 21, in one direction the gap can be increased g it in theopposite direction can be decreased.

For the purpose of securely locking the upper electrode in place, Iprovide a lock nut The bushing 24: is likewise externally threaded asindicated at 26 for coaction with the threads 13 of the porcelainopening- 13. By this means the upper electrode assembly, i. e. electrodeproper .21, bushing Zl and the parts carried thereby, can be screwedinto the porcelain element 4.

It is a purpose at iny'inyention to establish and maintainin'tho chamber20 of the shell 17 a predetermined conditioner status. It is notnecessary to detail the precise character or status to be maintained inthe space 20, but sutlice it to say that having determined upon thecondition which will lend the bestresults, I desire to maintain thatcondition or status against alteration or va riation. I might stategenerally that the function of the spaced relation of the upper andlower electrodes forming the-gap 22 is to increase the voltage of thespark that will jump'the gap 27 formed between the lower cnds oi thelower central electrode and the side electrode. At the same time, inbuilding up this'voltage condition extreme care must be cxerciscd toavoid imposing upon other parts of the electric or ignition of aninternal combustion engine of forces that would destroy or injure them.Thus, for example in a modern automobile ignition system care must betaken to avoid puncturing the com-lcnser and where a coil is used toavoid injuring the coil.

()n the other hand, it the desired results are to be attained thevoltage conditions nee cssary are relatively high. Thus it becomes animportant matter, indeed, after having determined that condition whichis sutlicient on one hand to secure the desired spark at the gap 27 andto avoid injuring other parts of the ignition system, to maintain thatpre dctcrmined desired condition or status. Que oi the most necessaryprecautions to this end is that of avoiding the seepage of the dead gasfrom thecngine cylinder up throu 'h the spark plug and into the chamber20. it has been the commonpractise to secure the cen tral clcctrodc inplace by means of cement and while such cement is presumed to beimpclvious to the passage of gases therethrough, in practise, it isfound to be porous 'to a certain extent, and, in fact, to an extent'sulator surrounding said such that unless other means he provided wouldpermit seepage of gas into the space surrounding the gap .22 and henceafter a time destroy, alter or modify tl'iat de sired conditioninitially set up in that space. I prevent the possibility of theoccurrence of such a result by the provision of ashell 17 which, asalready described, is united to the electrode in such a manner asabsolutely to insure a gas-tight joint, under all conditions. The upperend of the shell 17 is open and is provided with an outwardly extendingflange portion 28 which rests upon a seat 29 provided in the porcelaininsulator. For the purpose of closing the open end of the shell 17, Iprovide an insulator plug 30. This insulator plug is very tightlypressed against the top of the shell 17 by means of the threaded bushing26, i. e. as the threaded bushing 26 is screwed into the porcelaininsulator it forces the insulator plug 30, very tightly against theshell.

In assembling the device the shell 17 is pressed into the opening 12provided therefor, and being of soft character forms a fairly tightjoint. The gases from the engine cannot possibly find their way into thechamber 20. In the first place, any gases attempting to escape upwardlymust pass around innumerable turns or corners which in themselves shouldbatlle the progress of such gases. If it were possible for gases to findtheir way upwardly to the point above the shell 17, they would be unableto find their way into the chamber 20, for the reason that the insulatorplug 30 is very tightly clamped between the bushing 2% and the upperflanged end of the shell 17. The me chanical seal thus provided isadmirably adapted to the maintenance of the predetermined condition orstatus in the chamber 20, and at the same time the arrangement is suchthat if desired relative adjustment of the upper and lower centralelectrodes can be very readily and conveniently made.

I claim l. A spark plug construction embodying therein an insulatorelement, upper and lower electrodes arranged therein and posi tioncd toform a gap therebctwcen, an impervious metallic shell positioned in saidingap and lorming a chamber adapted to exclude gases inimical to thecondition desired in th space surrounding said gap, and mcans insulatingsaid upper and lower electrodes one fronrthc other.

2. spark plug construction embodying therein an insulator clement, upperand lower clcctrodcs arranged therein and positioncd to. l'orm a gaptherelmtwcen, an impclvious shell, formed of metal of softer characterthan that of the lower electrode, positioned in said insulator,surrounding said gap, and forming a chamber adapted to exclude gasesinimical to the condition desired in the, space surrounding said gap,and m *ans insulating said upper and lower electrodes one from theother. I

3. A spark plug construction embodying therein an insulator element,upper and lower electrodes arr: iged therein and positioned to form agap therebetween, a metallic shell initially having openings at bothends, said shell being shrunk upon the lower central electrode therebyclosing one opening, and an insulator plug pressed against the other endof said shell and closing the other opening, thereby forming a chambersurrounding said gap, said chamber being impervious'to gases inimical tothe condition desired in-the space surrounding said gap.

-l. A. spark plug construction embodying therein lower electrodesarranged therein and positioned to form a gap therebetween, a metallicshell initially having openings at both ends, said shell being shrunkupon the lower central elect-rode thereby closing one opening, and aninsulator plug pressed against the other end of said shell and closingthe other opening thereby forming a chamber surrounding said gap, saidchamber being impervious to gases inimical to the condition desired inthe space surrounding said gap, and a screw threaded element for torcingsaid insulator plug against said shell.

5. A spark plug construction embodying therein an insulator element,upper and lower electrodes arranged therein and positioncd to form a gapthercbetween, a me.- tallic shell initially having openings at both.-ends. said shell being shrunk upon the lower central electrode therebyclosing one opening. and an insulator plug pressed against the other endof said shell and closing that opening thereby forming achambersurrounding said gap, said chamber being impervious to gases inimical tothe condition desired in the space surrounding said gap, a screwthreaded element for forcing said insulator plug against said shell,said screw threaded element being internally threaded and the upper endof said upper central clcctrodc being cxtcrnally threaded, whereby theposition of said upper electrode, in said bushing can be adjusted.

o. spark plug construction embodying lhcrcin an insulator clement, upperand lower electrodes arranged therein and posilioncd to lornr a gaptherebetwcen, a metallic shcll initially having openings at both ends,said shell being shrunk upon the lower central electrode thereby closingone opening. and an insulator plug pressed against the other end of saidshell and closing the other opening, thereby forming a chambersurrouiuling said gap, said chamber being impervious to gases inimicalto the condian insulator element, upper and tion desired in the spacesurrounding said gap, a screw tln'emiled. element for forcing Saidlnsulahjn' plug against said shell, said screw threaded element beinginternally tln'ezutleclfl and the, upper end of said upper centralelectrode being externally threaded whereby the position of said upperelectrode in said bushing can be adjusted, end means for locking saidupper central elecfrode in adjusted position. 10

In testimony whereof, I have hereunto set my hand, this 22nd. day ofApril, A. D.

JGHN M. ATWATER.

